Composite Disturbance Rejection Control for Ball Balancer System

Abstract

2 Degree Of Freedom(2DOF) Ball Balancer system is a highly nonlinear system where the position of the ball is controlled by controlling two servo motors simultaneously. This system is an advanced version of ball and beam system 1 Degree Of Freedom (1 DOF). The physical significance of the ball balance system are pan and tilt cameras for surveillance and satellite position correction. In general conventional PID controller is used in order to control the position of ball on plate in both axes (X, Y). PID controller is used to obtain an acceptable satisfactory response of the system. However, an exact nonlinear compensator is included to assure the closed-loop system stability. The major issue of conventional PID cannot give good eliminated results when external disturbance is more. This problem can be improvised by implementing Disturbance observer enhanced PD or PID controller(DOB). In this work the performance of Disturbance observer(DOB) enhanced PD controller is compared with the conventional PD controller response. In DOB enhanced PD the observer used is the inverse of the system transfer function and it observes the externally applied disturbance and make the system response to perform better in an environment prone to disturbances. The results are illustrated via simulation.